linux-kernel - Re: [PATCH] mm/vma: small VMA lock cleanups

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Message-ID: <CAJuCfpG2f40hosmWVcgTs7O5jSgLNp8w4Mt50N2+t1k9CLLMtQ@mail.gmail.com>
Date: Mon, 27 Oct 2025 17:49:06 -0700
From: Suren Baghdasaryan <surenb@...gle.com>
To: Lorenzo Stoakes <lorenzo.stoakes@...cle.com>
Cc: Andrew Morton <akpm@...ux-foundation.org>, "Liam R . Howlett" <Liam.Howlett@...cle.com>, 
	Vlastimil Babka <vbabka@...e.cz>, Shakeel Butt <shakeel.butt@...ux.dev>, linux-mm@...ck.org, 
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] mm/vma: small VMA lock cleanups

On Fri, Oct 24, 2025 at 2:09 AM Lorenzo Stoakes
<lorenzo.stoakes@...cle.com> wrote:
>
> We declare vma_start_read() as a static function in mm/mmap_lock.c, so
> there is no need to provide a stub for !CONFIG_PER_VMA_LOCK.
>
> __is_vma_write_locked() is declared in a header and should therefore be static
> inline.
>
> Put parens around (refcnt & VMA_LOCK_OFFSET) in is_vma_writer_only() to make
> precedence clear.
>
> Signed-off-by: Lorenzo Stoakes <lorenzo.stoakes@...cle.com>

Thanks for cleaning this up!

Reviewed-by: Suren Baghdasaryan <surenb@...gle.com>

> ---
>  include/linux/mmap_lock.h | 7 ++-----
>  1 file changed, 2 insertions(+), 5 deletions(-)
>
> diff --git a/include/linux/mmap_lock.h b/include/linux/mmap_lock.h
> index 2c9fffa58714..e05da70dc0cb 100644
> --- a/include/linux/mmap_lock.h
> +++ b/include/linux/mmap_lock.h
> @@ -130,7 +130,7 @@ static inline bool is_vma_writer_only(int refcnt)
>          * a detached vma happens only in vma_mark_detached() and is a rare
>          * case, therefore most of the time there will be no unnecessary wakeup.
>          */
> -       return refcnt & VMA_LOCK_OFFSET && refcnt <= VMA_LOCK_OFFSET + 1;
> +       return (refcnt & VMA_LOCK_OFFSET) && refcnt <= VMA_LOCK_OFFSET + 1;
>  }
>
>  static inline void vma_refcount_put(struct vm_area_struct *vma)
> @@ -183,7 +183,7 @@ static inline void vma_end_read(struct vm_area_struct *vma)
>  }
>
>  /* WARNING! Can only be used if mmap_lock is expected to be write-locked */
> -static bool __is_vma_write_locked(struct vm_area_struct *vma, unsigned int *mm_lock_seq)
> +static inline bool __is_vma_write_locked(struct vm_area_struct *vma, unsigned int *mm_lock_seq)
>  {
>         mmap_assert_write_locked(vma->vm_mm);
>
> @@ -281,9 +281,6 @@ static inline bool mmap_lock_speculate_retry(struct mm_struct *mm, unsigned int
>         return true;
>  }
>  static inline void vma_lock_init(struct vm_area_struct *vma, bool reset_refcnt) {}
> -static inline struct vm_area_struct *vma_start_read(struct mm_struct *mm,
> -                                                   struct vm_area_struct *vma)
> -               { return NULL; }
>  static inline void vma_end_read(struct vm_area_struct *vma) {}
>  static inline void vma_start_write(struct vm_area_struct *vma) {}
>  static inline void vma_assert_write_locked(struct vm_area_struct *vma)
> --
> 2.51.0
>